Skid base for portable building

CROSS-REFERENCE TO RELATED APPLICATION

0001This application is a continuation of U.S. patent application Ser. No. 10/781,129 filed Feb. 18, 2004, issuing as U.S. Pat. No. 7,373,757 on May 20, 2008, which claims the benefit of U.S. Provisional Patent Application No. 60/448,567 filed Feb. 19, 2003 and is a continuation-in-part of U.S. patent application Ser. No. 10/195,680 filed Jul. 12, 2002, issued as U.S. Pat. No. 6,823,639 on Nov. 30, 2004, which is hereby incorporated by reference, and which claims the benefit of U.S. Provisional Application No. 60/346,641 filed Jan. 8, 2002, and is a continuation-in-part of U.S. patent application Ser. No. 09/504,513 filed Feb. 15, 2000, issued as U.S. Pat. No. 6,418,672 on Jul. 16, 2002, and which claims the benefit of U.S. Provisional Application No. 60/120,828 filed Feb. 19, 1999.

STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

0002Not applicable.

FIELD OF THE INVENTION

0003This invention relates generally to a plastic resin building, for example, an outhouse or bus stop, and in particular to a skid base for such a building.

BACKGROUND OF THE INVENTION

0004Outdoor shelter structures, such as portable outhouses, are commonly rented and used for special events, such as parties, festivals or concerts, as well as at job sites or other locations where people are gathered temporarily. These shelters are moved to and from the site on a truck typically, and while at the site they may be pumped out occasionally, to empty their septic tanks. While at the site, they must be stable, and not susceptible to tipping over, or being tipped over by the wind or by vandals.

0005These shelters must be rugged and durable, and since they must be moved manually, most operators who rent these out (a.k.a., pumpers) prefer them to be light in weight. A minority want them heavy, so as to counter any tendency to tip over. The buildings must be movable on and off of the truck, but once off of the truck, a single person should be able to move the building across the ground to position it in the desired location. The buildings also must be low in cost.

0006It is common to form much of these outdoor shelters of plastic resin. One exception, however, has been the base on which the remainder of the building is built. The bases are typically a composite structure of plastic and wood. The bases also usually have several main structural components, which can adversely affect their strength and rigidity.

0007Another common problem has been the connections between the shelter walls and the base. While plastic components in the base are preferable to wood for aesthetics, cleanliness and durability, the fastener holding ability of plastic base components has often been lacking. Sheet metal screws are typically used to secure the shelter walls to the base. The stresses at these fastener locations can be great when moving the shelter, under heavy winds, or when forces are applied to the walls, especially with a person in the shelter or with a full septic tank. Failure of the base to hold the fasteners can result in troublesome or costly repairs or complete replacement of the base or whole shelter.

SUMMARY OF THE INVENTION

0008The present invention provides a resin skid base for a portable building that overcomes the aforementioned problems.

0009A skid base of the invention has a deck with top and bottom surfaces, and front, rear, right, left and side surfaces between the top and bottom surfaces, the skid base being adapted to mount walls of a building structure that extend above and enclose the top surface of the deck. The skid base has at least two runners that are generally parallel and spaced apart and extend beneath the deck, each runner having a bottom surface to support the deck above a support surface. The runners and the deck are molded in one piece so as to be integral with one another and have openings in their bottom surfaces that open downwardly. This provides a skid base that is enclosed on all sides but the bottom. The bottom of the base is not visible in normal use as it faces the ground, and can be formed with reinforcement ribs and covered with other parts if necessary, which can be replaceable.

0010The invention may be applied to skid bases that may be used for buildings with different purposes, such as outhouses, bus stop shelters, ticket booths, sentry huts and storage sheds. If used as an outhouse, the base supports a septic tank, and the base is shaped to match the bottom of the tank which is sloped toward a central, low point of the tank to facilitate pumping out the tank.

0011Thus, the invention provides an improved resin skid base for a portable building that can be used for many purposes. The base is easy to assemble and disassemble to the remainder of the building and is lightweight with all of its main structural components integrally formed in one piece for excellent strength and rigidity. Runners of the base have solid vertical walls and have openings in the bottoms in which reinforcing ribs are formed. A bottom plate is assembled to the skid over the opening to close the opening and provide a continuous surface to slide over the ground like a ski, to facilitate moving the building over the ground. Notches are formed into the runner sidewalls and in the bottom plates to catch on the edge of a truck so the building can be more easily loaded onto and unloaded from the truck. The bottom plates also have a longitudinal groove in which the fastener heads that hold the plate to the runner are countersunk, that rigidifies the runner and plate, and that reduces friction when the building is slid over the ground. The runners and plates also have stake down slots to allow anchoring the building with stakes at an angle and reinforcing ribs in the plates in the areas of the truck loading notches.

0012In another aspect of the invention, an open grate-type floor is molded into and integrally part of the deck. This is ideal for construction sites or outdoor concert-type events where a lot of dirt is carried on the bottom of the user's shoes into the building. It also helps keep the building clean in normal use, as fluids and small objects can drop through the grate. Ventilation is also improved through the grate. When a solid floor is required, a thin sheet of plastic can be placed over the grate to close it.

0013Preferably, the floor is crowned in the center to allow liquids to run off if the open grating is covered with the plastic sheet.

0014In addition, the openings in the grating are preferably tapered such that if anything is dropped or forced into the hole from the top, it is assured of dropping down through the bottom. The webbing, or ribs, that create the grating are taller at the perimeter of the floor than at the center to save weight and maintain strength.

0015Another feature of the invention is that it is provided with cabin mounting fastener locaters. These are lines molded into the sides of the upper base and on the top surface of the runners to show where to put the threaded fasteners to mount the cabin wall panels. The material of the base is thicker in these places. In addition, bosses that provide fastening points for the fasteners that secure the wear plates to the runners can be coincident in location to these places.

0016In one preferred form, the base is adapted for use as the base of a portable restroom, and in that case, the surface of the base that supports the waste or septic tank is molded to conform to the bottom of the tank. The bottom of the tank is slanted downwardly toward a central point in the bottom of the tank. There are, therefore, no flat surfaces or pockets to prevent complete drainage to the bottom of the tank, which facilitates pumping the waste out of the tank. In addition, in this embodiment, there may be provided triangular-shaped reinforcements at the corners, to give the base unit corners strength and dimensional stability. Preferably, these reinforcements are also sloped down to match the shape of the septic tank.

0017A base of the invention may be injection molded using high density polyethylene structural foam material, in which case it would be relatively light in weight. Many pumpers prefer a light weight structure, for ease of transport. However, there are some who prefer it to be heavier. To satisfy them, additional weight bars, for example, made of iron or another heavy material, can optionally be added to the base, and in addition weight covers may be provided to cover the weights or to close up the bottom of the base if so desired.

0018The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

0019<figref idref="DRAWINGS">FIG. 1</figref> is a right front perspective view of a portable restroom incorporating a base of the invention;

0020<figref idref="DRAWINGS">FIG. 2</figref> is a top plan view of the base alone;

0021<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional view taken along the plane of the line <b>3</b>-<b>3</b> of <figref idref="DRAWINGS">FIG. 2</figref>;

0022<figref idref="DRAWINGS">FIG. 4</figref> is cross-sectional view taken along the plane of the line <b>4</b>-<b>4</b> of <figref idref="DRAWINGS">FIG. 2</figref>;

0023<figref idref="DRAWINGS">FIG. 5</figref> is cross-sectional view taken along the plane of the line <b>5</b>-<b>5</b> of <figref idref="DRAWINGS">FIG. 2</figref>;

0024<figref idref="DRAWINGS">FIG. 6</figref> is a bottom plan view of the base of the invention shown with the bottom plates and weight covers and weights removed;

0025<figref idref="DRAWINGS">FIG. 7</figref> is a bottom perspective view of the base;

0026<figref idref="DRAWINGS">FIG. 8</figref> is a fragmentary detail view of the indicated portion of <figref idref="DRAWINGS">FIG. 7</figref>;

0027<figref idref="DRAWINGS">FIG. 9</figref> is a bottom plan view of the base illustrating the rib pattern of the deck and other features;

0028<figref idref="DRAWINGS">FIG. 10</figref> is a perspective view illustrating the bottom plates exploded from the runners of the base;

0029<figref idref="DRAWINGS">FIG. 11</figref> is a detail view of the indicated portion of <figref idref="DRAWINGS">FIG. 10</figref>;

0030<figref idref="DRAWINGS">FIG. 12A</figref> is a sectional view taken along line <b>12</b>A-<b>12</b>A of <figref idref="DRAWINGS">FIG. 2</figref> with the bottom plate exploded from the runner of the base;

0031<figref idref="DRAWINGS">FIG. 12B</figref> is a cross-sectional detail view of the indicated portion of <figref idref="DRAWINGS">FIG. 12A</figref>, taken at 90° from the plane of <figref idref="DRAWINGS">FIG. 12A</figref>;

0032<figref idref="DRAWINGS">FIG. 13A</figref> is a top perspective view of the bottom plate;

0033<figref idref="DRAWINGS">FIG. 13B</figref> is a cross-sectional view from the plane of the line <b>13</b>B-<b>13</b>B of <figref idref="DRAWINGS">FIG. 13A</figref>, with the bottom plate mounted on the base;

0034<figref idref="DRAWINGS">FIG. 14</figref> is a perspective view of the base with a plastic sheet covering the grates of the deck;

0035<figref idref="DRAWINGS">FIG. 15</figref> is a detail fragmentary cross-sectional view showing the plastic sheet on top of the deck;

0036<figref idref="DRAWINGS">FIG. 16</figref> is a front plan view of the base;

0037<figref idref="DRAWINGS">FIG. 17</figref> is a cross-sectional view of the base from the plane of the line <b>17</b>-<b>17</b> of <figref idref="DRAWINGS">FIG. 16</figref>;

0038<figref idref="DRAWINGS">FIG. 18</figref> is a detail view of the indicated portion of <figref idref="DRAWINGS">FIG. 17</figref>;

0039<figref idref="DRAWINGS">FIG. 19</figref> is a cross-sectional view from the plane of the line <b>19</b>-<b>19</b> of <figref idref="DRAWINGS">FIG. 2</figref>;

0040<figref idref="DRAWINGS">FIG. 20</figref> is a cross-sectional view from the plane of the line <b>20</b>-<b>20</b> of <figref idref="DRAWINGS">FIG. 19</figref>;

0041<figref idref="DRAWINGS">FIG. 21</figref> is a bottom exploded perspective view of the base illustrating the bottom plates, weights and weight covers exploded from the base; and

0042<figref idref="DRAWINGS">FIG. 22</figref> is a perspective view of the weights.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0043<figref idref="DRAWINGS">FIG. 1</figref> illustrates a resin building <b>10</b> which as illustrated is a portable outhouse, and includes a base <b>12</b> of the present invention and a cabin <b>14</b> having sides and a roof, the cabin <b>14</b> being bolted to the base <b>12</b> with fasteners <b>16</b> on both sides thereof, and optionally also on the front and back.

0044The cabin <b>14</b> may be of any suitable construction and is not limited to being a portable outhouse. For further details about the construction of a suitable cabin <b>14</b>, reference is made to U.S. patent application Ser. No. 10/195,680 (US Patent Publication No. 2003/0024191 published Feb. 6, 2003) and to U.S. Pat. No. 6,418,672, which are incorporated herein by reference.

0045Referring to <figref idref="DRAWINGS">FIGS. 2-9</figref>, the base <b>12</b> has a deck <b>18</b> integral with two spaced apart generally parallel runners <b>13</b> that are molded integrally in one piece with the deck <b>18</b> by an injection molding process using high density polyethylene structural foam. High density polyethylene structural foam is preferred since it is a strong and relatively lightweight plastic material which can be molded using aluminum molds, which are considerably less expensive than steel molds. Impact modifiers such as ethyl vinyl alcohol (EVA) may be added to the material to improve impact resistance, other additives may be added for other properties, or a different basic material such as low density polyethylene or another material may be used.

0046One preferred aspect of the base design is the direction that the mold splits apart to yield a base that is formed on all sides with molded surfaces (top, front, rear, left and right sides) except the bottom side. The bottom side of the base (i.e., the bottom sides of the deck <b>18</b> and runners <b>13</b>) is not visible in normal use as it faces the ground. In addition, the openings on the bottom of the base, where they are important, can be closed up with other parts, that can be replaced when they wear out. Another advantage of making the openings on the bottom of the base is that numerous structural reinforcement ribs can be provided, which serve to strengthen the various portions of the base, as illustrated in <figref idref="DRAWINGS">FIGS. 2-9</figref>.

0047As shown in <figref idref="DRAWINGS">FIGS. 10-13B</figref> and <b>21</b>, a wear plate <b>20</b> is provided which covers the bottom opening of each runner <b>13</b>. The runner wear plate <b>20</b> is smooth on the bottom so that it can be pushed over an uneven ground surface. The wear plate <b>20</b> closes the opening in the bottom of the runners <b>13</b> to cover the numerous ribs and webs placed throughout the runners <b>13</b> for strength. Without the runner wear plates installed, these webs and ribs would be visible and the skid base would not be functional, i.e. it would be too hard to push the building over an uneven ground surface. The runner wear plates <b>20</b> can also be replaced should they become too worn down or damaged. The runner wear plates <b>20</b> are affixed to the runners <b>13</b> by self threading fasteners <b>21</b> (<figref idref="DRAWINGS">FIG. 21</figref>, shown on only one side) extending through the holes <b>22</b> (<figref idref="DRAWINGS">FIG. 11</figref>) into the holes <b>24</b> (<figref idref="DRAWINGS">FIG. 9</figref>), five or so of which are provided for each wear plate/runner. More (or less) may be added, depending on how many are desired or needed to hold the wear plates <b>20</b> on.

0048At each location where a hole <b>24</b> is formed, there are lines <b>26</b> (e.g., small grooves) molded into the sides of the deck <b>18</b> and on the top surface of the runners <b>13</b> to show where to put the threaded fasteners for mounting the cabin panels, i.e. for mounting the cabin front, sides, and rear. The structural foam material of the deck <b>18</b> is thicker in these locations, a result of the placement of the bosses <b>28</b> that contain the holes <b>24</b> that provide the fastening points for the runner wear plates <b>20</b>. Referring to <figref idref="DRAWINGS">FIG. 8</figref> and <figref idref="DRAWINGS">FIGS. 17-20</figref>, the generally cylindrical boss <b>28</b> in which the hole <b>24</b> is formed, extends all the way to the underside of the top of the base so as to substantially fill the void on the inside of side wall <b>30</b> at the location of line <b>26</b>. Thereby, a self threading fastener <b>16</b> can be driven into the side wall <b>30</b> at the line <b>26</b> and be substantially fully engaged to a depth significantly greater than the thickness of the sidewall <b>30</b> by the material of the deck <b>12</b>, i.e., to a depth approximately equal to the lateral dimension of the boss <b>28</b>. Triangular reinforcing structures provided by ribs <b>29</b> (<figref idref="DRAWINGS">FIG. 9</figref>) provide additional reinforcement by tying the bosses <b>28</b> into the inner sidewall <b>31</b>, and provide additional thickness where the ribs <b>29</b> intersect the boss <b>28</b> for the fasteners <b>16</b> to penetrate.

0049In addition, referring particularly to <figref idref="DRAWINGS">FIGS. 11</figref>, <b>12</b>A, <b>12</b>B, <b>13</b>A, <b>13</b>B and <b>21</b>, each end of each runner <b>13</b>, and in the corresponding locations of each wear plate <b>20</b>, a notch <b>32</b> in the runners <b>13</b> and notch <b>34</b> in the wear plates <b>20</b> is formed which serves as a truck mounting notch. As is known in the art, these notches are used for hooking onto the edge of a truck or trailer bed to keep the building from slipping while loading and unloading. Solid ribs <b>36</b> and <b>38</b> are formed in the areas of the notches <b>34</b> to strengthen the wear plates <b>20</b> and runners <b>13</b> in these locations. In addition, elongated stake down slots <b>40</b> and <b>42</b> are provided at each corner of the respective runner <b>13</b> and wear plate <b>20</b> which are diagonally oriented to provide the maximum holding power of the stakes. By making them elongated and diagonally oriented, the stakes can be driven in at an angle toward the center of the restroom oblique to the natural tipping direction of the restroom, to hold the restroom against the ground in high wind or when vandals are trying to tip it over.

0050In addition, referring particularly to <figref idref="DRAWINGS">FIG. 13A</figref>, the wear plate <b>20</b> has a longitudinally running channel <b>46</b> that runs for the length of the wear plate. The channel <b>46</b> acts as a stiffening shape, without adding significant material thickness to the wear plate <b>20</b>. Since it is indented on the bottom surface of the runner <b>20</b>, the channel <b>46</b> also reduces the contact with the ground thereby making it easier to move the building <b>10</b> when sliding it along the ground on the wear plates <b>20</b>. The channel <b>46</b> also provides a countersink area for the heads of the fasteners <b>21</b> which are used to hold the wear plates <b>20</b> to the runners <b>13</b>.

0051It should be noted that the base <b>12</b>, the wear plates <b>20</b>, and also optional weight cover plates <b>71</b> which can be provided over the weight holding areas of the base <b>12</b>, described below, can be molded in a single family mold, all at the same time. The skid base <b>12</b> can be made in a standard size, for example, a 41 inch by 41 inch industry standard size, which will fit most portable restrooms produced currently.

0052Another preferred feature of the base <b>12</b> is that the deck <b>18</b> is provided with a grate style floor <b>52</b> that has a grid of openings formed in it. Since one mold half is inserted into the bottom of the base, and the other mold half forms the top of the base, the draft on the bottom mold half makes the openings of the grate larger at the bottom than at the top, so that anything falling through the grate <b>52</b> from the top will be sure to fall all the way through and not get caught in the bottom of an opening. In addition, referring particularly to <figref idref="DRAWINGS">FIG. 9</figref>, it is noted that some of the ribs that form the grate are of constant height for their length, for example, the ribs <b>50</b>, and others, the ribs <b>53</b>, are arched so that they are of smaller height in their central portions than at their ends. Making the ribs or webbing that creates at least some of the grating ribs higher at the perimeter than at the center saves weight while at the same time maintaining strength in the grate style floor <b>52</b>. Alternatively, the ribs <b>53</b> could be made of a uniform height for their length, or the bottoms of the ribs <b>53</b> could be all at the same height (in the same plane), like the ribs <b>50</b>.

0053Another advantage of the grate style floor <b>52</b> is that it improves ventilation through the building, which is particularly important when it is used as an outhouse, and as mentioned above, dirt, rocks and urine falls through the grate <b>52</b>.

0054Referring to <figref idref="DRAWINGS">FIG. 12</figref>, the upper surface <b>58</b> of the grate style floor <b>52</b> is arched or crowned in the front to back direction to allow liquids to run off, which is particularly important if the open grating is covered with a plastic sheet, as may be done as shown in <figref idref="DRAWINGS">FIG. 14</figref>, the sheet being referred to as item <b>60</b>. The sheet <b>60</b> may be desirable if anyone with high heels may be expected to use the building, or if the building is used for something other than a restroom, particularly in cold weather.

0055Referring to <figref idref="DRAWINGS">FIGS. 2-4</figref>, when the base <b>12</b> is used as the base of a restroom, the deck <b>18</b> defines an opening <b>62</b> at its rear, behind the floor <b>52</b>, in which the holding or septic tank <b>63</b> (<figref idref="DRAWINGS">FIG. 1</figref>) is placed. The bottom of the septic tank <b>63</b> is sloped so that its lowest point is right beneath the seat hole in the top of the tank <b>63</b>. This is so that the tank <b>63</b> can be easily pumped out. To accommodate the sloping bottom wall of the tank <b>63</b>, the top edges that define the opening <b>62</b> are slanted inwardly toward the ground as shown in <figref idref="DRAWINGS">FIGS. 3 and 4</figref> at <b>64</b>, <b>66</b>, <b>68</b>, and <b>70</b>. In addition, where the slanted edge <b>68</b> at the rear of the base meets the slanted side edges <b>66</b> and <b>70</b>, the corners <b>72</b> and <b>74</b> are triangular-shaped (in top plan view) to give the corners strength and dimensional stability. Since the corners <b>72</b> and <b>74</b> are formed by the slanted surfaces <b>68</b>/<b>66</b> and <b>68</b>/<b>70</b>, they funnel toward the center of the opening <b>62</b> with the intersection between the surfaces <b>66</b> and <b>68</b> and between the surfaces <b>70</b> and <b>68</b> defined by junction lines <b>76</b>.

0056Referring to <figref idref="DRAWINGS">FIGS. 7</figref>, <b>21</b> and <b>22</b>, for those applications where it is desired that the base <b>12</b> be made heavier, weights <b>77</b> may be added into the laterally running openings <b>80</b> and <b>82</b> formed at the respective front and rear edges of the floor <b>52</b> and which open toward the bottom of the base <b>12</b>. Forming these is another advantage of molding the base <b>12</b> with a parting line between the mold halves which is generally horizontal with respect to the normal use of the base <b>12</b>. The openings <b>80</b> and <b>82</b> each are formed with a number of bosses <b>84</b> that match the holes <b>74</b> formed in bar weights <b>77</b> (<figref idref="DRAWINGS">FIGS. 21 and 22</figref>) which are made of iron, steel, or another heavy material. Self threading fasteners <b>73</b> (two shown at the rear in <figref idref="DRAWINGS">FIG. 21</figref>) extend through the holes <b>74</b> into the bosses <b>84</b> to secure the weights <b>77</b> in the recesses <b>80</b> and <b>82</b>. Covers <b>71</b> (<figref idref="DRAWINGS">FIG. 21</figref>) may also be provided for the openings <b>80</b> and <b>82</b>, which as stated above may be formed in the same mold as the base <b>12</b> and wear plates <b>20</b>, and may be secured over the openings in <b>80</b> and <b>82</b> by the same fasteners <b>73</b> that secure the weights.

0057A base of the invention has its runners formed integral with the deck and other structural components of the base in a molding process which forms all of the recesses of the deck and runners opening downwardly. This enables using ribs, bosses, and draft angles in the recesses which are not visible to users and which contribute to an efficient, economical, high-strength, and rigid molded base.

0058A preferred embodiment of the invention has been described in considerable detail including many particular preferred features. Many modifications and variations to the preferred embodiment described, and to the features of it, will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiments described or to the particular features of it, but should be defined by the claims which follow.